Lighting coop to induce egg laying?

Hi! Newbie here I have a question about using artificial light to get my hens to lay. My hens include a few barnyard mutts I hatched out of neighbors eggs this past April, a barred rock hen we found in the work parking lot ( long story lol) and 3 white leghorn hens. My rooster is a gentle buff orphington. The young mutts haven't started laying yet, and my leghorns completely stopped a few weeks ago (they went through a move, they were my mothers and they stopped laying so she didn't want them anymore). Today is day 8 of having a light in my coop, its on a timer and they are getting 18 hours of light a day, because I read in a different thread that is what they should get if they aren't laying. My question is, how long should it take for them to start laying with the help of the lighting? So that I can know if the lighting is the issue or if I have to try something else.

It sounds like your girls have had to move around a bit...chickens don't adapt to changes quickly so give them time to re-settle. Can you give us an idea of what you are feeding your flock? Have your older girls been molting? Is everyone in good health?

There could be reasons other than fewer daylight hours that has caused your older girls to stop laying is what I'm trying to get at. As long as everyone is healthy, I wouldn't be too concerned. Personally, I never used artificial light in our coop...I figure they work hard almost all year long and deserve a rest and they'll lay when they are ready to lay.

I don't have an answer to your question about how much time has to elapse before they resume laying more regularly. I do know there is a potential cost to giving the, article light. Also, I understand 14 hours per day is necessary for steady production...unsure what 18 hours does. That and other factors about adding light to the coop are explained in this link: https://www.backyardchickens.com/a/chickens-winter-egg-laying-and-lighting
Best wishes!